PHA First Exam Fall 2013

Transcription

1 PHA 5127 First Exam Fall 2013 On my honor, I have neither given nor received unauthorized aid in doing this assignment. Name Question Set/Points I. 30 pts II. III. IV 20 pts 20 pts 15 pts V. 25 pts VI. VII. VIII. IX. 20 pts 15 pts 20 pts 35 pts TOTAL: 200 pts 1

2 Question Set I (True or False) (30 points) True (A) or False (B). On the bubble sheet mark A for true or B for false. Assume passive diffusion as the driving force for distribution. 1: T F Assume a drug that is eliminated through metabolism. The drug s plasma concentration decreases by 2 ng/ml every 2 hours. This is a first order process. 2: T F Assume a drug eliminated through enzymatic metabolism. The drug s plasma concentration decreases by 2 ng/ml every 2 hours. The elimination rate constant describing this metabolism will be unit-less 3: T F The rate with which a lipophilic drug of low molecular weight that is not an acid nor a base is taken up by tissues will significantly be related to the blood flow through those tissues. 4: T F The rate with which a lipophilic drug that is not an acid nor a base is taken up by brain and liver tissue is likely to be similar, as the drug will be able to cross membranes in both tissues very fast. 5: T F An intravenous bolus injection (iv bolus) is often given to the patient to achieve high blood concentrations immediately. 6: T F To prepare plasma, blood is often collected in tubes containing calcium chloride 2

3 Question Set II (20 points) True (A) or False (B). On the bubble sheet mark A for true or B for false. Consider a lipophilic drug A and a protein drug (drug B, e.g. antibody). Both do not show any affinity to transporters (Ficks law applies). They both don t bind to plasma and tissue components. 7: T F Drug A will enter the brain faster. 8: T F Drug B will be unable to enter the interstitial fluid. 9: T F Both drugs will have the same volume of distribution. 10: T F The volume of distribution of drug B will be 38L. 3

4 Question Set III (20 points) 11: Listed in the Table are two properties of acidic drug molecules: the fraction unionized at ph=7.4 and the partition coefficient of the unionized form. DRUG Fraction Unionized at ph=7.4 Partition Coefficient of Unionized form Molecular Weight (Dalton) Not determined 75, Select the correct rank order with which drugs 1-4 will enter brain tissue. Assume that the drugs are not subject to transporters at the blood-brain barrier. A: 1 slower than 2 slower than 3 slower than 4 B: 1 slower than 3 slower than 2 slower than 4 C: 4 slower than 2 slower than 3 slower than 1 D: 4 slower than 2 slower than 1 slower than 3 E: None of the above 4

5 Question Set IV (True or False) (15 points) True (A) or False (B). On the bubble sheet mark A for true or B for false. Assume no active transport. Assume the same dose of penicillin G is given to patients as iv bolus injection (as solution in saline), intramuscular (i.m.) oily injection or orally. 12: T F Giving the drug through an i.m. injections will result in a much smaller AUC than after oral administration 13: T F Giving penicillin as an aqueous intravenous bolus injection will result in a higher maximum concentration 14: T F oily i.m. injections allow a less frequent dosing. 5

6 Question Set V (True or False) (25 points) Conc. (ng/ml) Time (h) Conc. (ng/ml) Time (h) Drug A Drug B True (A) or False (B). On the bubble sheet mark A for true or B for false 15: T F Drug A s rate of elimination is affected by the amount of drug in the body. 16: T F Drug B s elimination rate constant has the unit ng/ml. 17: T F For Drug A, the fraction of drug eliminated per hour is constant. 18: T F Drug A s concentration-time profile depends on the availability of sufficient number of enzymes (no saturation of the enzymes) 19: T F The half-life of Drug B is 5 hours. 6

7 Question Set VI (20 points) 20: 200 mg of Drug A was administered to a patient through i.v bolus injection. A plasma drug concentrations of 0.78 mg/l was measured after 4 hours. A plasma drug concentration of mg/l was measured after 8 hours. The drug s distribution is instantaneous. Assuming a first order process, calculate the half-life of the drug. A) 1 h B) 1.5 h C) 2 h D).34 h E) None of the above 21: 200 mg of Drug A was administered to a patient through i.v. bolus injection. A plasma drug concentrations of 0.78 mg/l was measured after 4 hours. A plasma drug concentration of 0.195mg/L was measured after 8 hours. The drug s distribution is instantaneous. Assuming a zero order process, calculate the drug concentration after 12 hours. A) 0 mg/l B) mg/l C) mg/l D) None of the above 7

8 Question Set VII (15 points) A drug (lipophilic, unionized, low molecular weight) is showing in average a pronounced binding to plasma proteins of 99%. Between-subject variability of protein binding is pronounced. The same dose of the drug is given as an i.v. bolus injection to two patients. Patient 1 has a much stronger plasma protein binding for the drug (99.95%) than the second patient (99.5%) The tissue binding is identical in both the patients (90%). Please indicate whether patient 1 will have a larger ( ), smaller ( ) identical ( ) value than patient 2 for: total initial total plasma drug concentration (Co), free initial total plasma drug concentration (free Co), f u V d 22 : A: C 0, free C 0, f u, V d B: C 0, free C 0, f u, V d C: C 0, free C 0, f u, V d D: C 0, free C 0, f u, V d E: none of above combinations. 8

9 Question Set VIII (20 points) Assume a drug is substrate of a specific transport protein. What of the following statements are True (A) or False (B). On the bubble sheet mark A for true or B for false 23 T F Transporters do not use energy 24 T F Transporters only eliminate intact drugs and not metabolites from the body 25 T F Transporters can be the reason for drugs not able to cross the blood brain barrier. 26 T F The low oral bioavailability of some drugs is due to the fact that transporters prevent absorption of the drug from the GI tract. 27 T F Assume a membrane separating the blood stream and the GI tract. These membranes express transporters that generally prevent absorption of orally given drugs (drug that crosses membranes are pumped out again). These transporters are not relevant for the elimination of the drug when administered through intravenous bolus injection. 9

10 Question Set IX (35 points) 28: T F Free drug concentrations are assumed to be the same in plasma and tissues, when the distribution is assumed to be instantaneous. 29: T F Gentamycin (a small molecular weight drug) has a volume of distribution of about 18L. Assume fu=fut. This drug is likely to be hydrophilic. 30: T F When the Vd of a drug is 700 L, This is only possible if the plasma protein binding is small. 31: T F A fast absorption might allow less frequent dosing. 32: T F A slower absorption might be advantageous for a drug with a narrow therapeutic window. 33: T F Pharmacokinetics can be used for optimizing drug therapy in a patient, as free drug concentrations in plasma and tissue are generally the same. 34: T F The larger the volume of distribution the smaller the starting concentration (Co) after an i.v. bolus injection. 10

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